Devicetree: Initialization order of mmc block devices?
eric.nelson at boundarydevices.com
Wed Jul 18 10:54:43 EDT 2012
On 07/18/2012 07:11 AM, Knut Wohlrab wrote:
> On 07/18/2012 03:47 PM, Jassi Brar wrote:
>> On 18 July 2012 15:19, Knut Wohlrab <knut.wohlrab at de.bosch.com> wrote:
>>> If a SD card is inserted at boot time, its "mmcblk0", the embedded
>>> MMC (eMMC) device "mmcblk1". This makes it difficult to give the kernel the
>>> correct device for the eMMC root file system ("root=/dev/mmcblk?p1 ...").
>> How about root=UUID=<eMMC-partition> ?
> Because we are talking about an embedded device, it is very difficult to get a
> UUID of a eMMC partition into kernel command line with U-Boot. Handling of UUID
> is also a big effort at board manufacturing.
> Startup speed is very important for us. Searching for UUID on several MMC/SD
> devices will significant slow down the boot process.
> This problem can occur on many devices with embedded MMC and removable SD, e.g.
> smart phones. So I think we should find an solution to define MMC scan order or
> device number/name in a device tree.
Isn't /dev/disk/by-path what you're after?
~$ ls -l /dev/disk/by-path/
lrwxrwxrwx 1 root root 13 Jan 1 15:22 platform-mmc0:b368 ->
lrwxrwxrwx 1 root root 15 Jan 1 15:22 platform-mmc0:b368-part1
lrwxrwxrwx 1 root root 15 Jan 1 15:22 platform-mmc0:b368-part2
lrwxrwxrwx 1 root root 15 Jan 1 15:22 platform-mmc0:b368-part3
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